A porous base matrix is used for a wide variety of adsorbents, such as an adsorbent for chromatography and an affinity adsorbent. Specifically, an affinity adsorbent is able to efficiently purify a target substance and reduce the content of unwanted substances, and is therefore used as a medical adsorbent and an adsorbent for purifying antibody drug. In particular, attention has been focused on adsorbents obtained by immobilizing protein A as an affinity ligand on a porous base matrix as medical adsorbents for the treatment of rheumatism, hemophilia and dilated cardiomyopathy (for example, Non-patent Document 1 and Non-patent Document 2).
Meanwhile, the adsorbent obtained by immobilizing protein A as an affinity ligand on a porous base matrix, i.e. adsorbents for purifying antibody drug, has attracted attention as an adsorbent able to specifically adsorb and release immunoglobulin (IgG). A method for immobilizing a variety of affinity ligands such as protein A on a porous base matrix can be selected from among a variety of immobilization methods, such as cyanogen bromide method, trichlorotriazine method, epoxy method and tresyl chloride method, described in Table 8.1 and FIG. 8.15 of Non-patent Document 3. In particular, it is preferable from an industrial perspective to use the reaction between a formyl group on a porous base matrix and an amino group on an affinity ligand so as to effect immobilization in terms of safety and for reasons such as the ease of the immobilization reaction and the fact that it is possible to use proteins or peptides produced by a relatively simple method.
As a method for introducing formyl groups in a porous base matrix, a method in which a polysaccharide gel having vicinal hydroxy groups is oxidized using periodate oxidation so as to generate formyl groups on the sugar chain can be used (for example, refer to Non-patent Document 4). The porous base matrix is hereinafter abbreviated to a “sugar chain cleavage-type” porous base matrix. An adsorbent obtained via the method has the advantage of having little ligand leakage.
In addition, it is possible to use a method that introduces formyl group via a variety of spacers obtained by, for example, a method that uses glutaraldehyde or a method in which periodate is made to act on glyceryl group obtained through the ring opening of epoxy group, which are disclosed in FIG. 8.15 of Non-patent Document 3 or Non-patent Document 5. The porous base matrix is hereinafter abbreviated to a “spacer-type” porous base matrix. The adsorbent produced by using the spacer-type formyl group-containing porous base matrix tends to have relatively high adsorption of a target substance. In addition, a method in which an amino sugar is introduced in an epoxy group of a porous particle and the amino sugar part is oxidatively cleaved to obtain a formyl group and an amino group-containing ligand is immobilized to the formyl group is described in Patent Document 1.